The invention relates to a device for use in business machines, data or teleprinters, and the like, for adjusting the height of the ribbon guide thereof at the printing station, whereby it may assume any one of a plurality of operating positions, or a visibility position in which the printing station of the machine is visible.
Where typewriters are provided with a ribbon which can be used only along a single line or track, relatively simple gearing can be provided to convey the ribbon from such a visibility position into an operating position for the printing of characters. A considerably greater complexity of gearing must be provided if one of two ribbon tracks is to be selectively operable, i.e. for example one track for black imprinting and one track for red imprinting. An equally expensive and complex gear construction is also required for use with carbon ribbons, in which, to effect a better exploitation of the ribbon, it is to be adjustable into a plurality of useful tracks.
Thus, it is known, for example from CH Patent 422,017, to continuously raise the ribbon on various useful tracks starting from the lower or bottom track. The variable range is achieved by means of a ratchet wheel which, with each stop, rotates a gear or wheel by one tooth pitch and thus displaces the translation fulcrum of the structure for effecting the lifting of the ribbon fork by small increments. However, it is also known, for example from U.S. Pat. No. 3,302,766, to alternately adjust the ribbon fork out of a visibility position into one of two levels or positions, which movements are executed by a ratchet wheel and a cam. A device is also known from German Patent No. 1,179,955 in which a cam plate is provided with a plurality of cam faces, one of which is selected by differently adjustable ratchets.
A common feature of all such arrangements is that mechanical gear elements requiring a relatively high production outlay are utilized to perform the functions required to effect an adjustment of the position of the ribbon guide. As a plurality of interengaging gear elements are generally required, disturbances due to mechanical influences and wear are likely. The requisite servicing and possible repair work involved are extremely costly.